Holder for piezoelectric crystals



1945' c. s. COCKERELL HOLDER FOR PIEZO-ELECTRIC CRYSTAL Filed Feb. 16,1944 IIHZYYF INVENTOR. GMe/sroP/me ,Sr 4 Cad/men;

A TTORNEY Patented Aug. 14, 1945 HOLDER FOR PIEZOELECTRIC CRYSTALSChristopher Sydney Cockerell, Chelmsford, England, assignor to RadioCorporation of America, a corporation of Delaware Application February16, 1944, Serial No. 522,583 In Great Britain November 10, 1942 Claims.

The present invention relates to holders for piezo-electric crystals. Itprovides such a holder which is particularly useful for use in mobileradio stations, such as aircraft and so forth, where the crystal may besubjected to considerable vibration.

.According to the invention, a holder for a piezoelectric crystalincludes at least one pair of rollers adapted to hold between them apiezo-electric crystal in such manner that one roller engages thecrystal on its one face and the other roller engages the crystal on itsother face, said one roller being rigidly fixed to a support and theother being spring urged towards said one roller so as to grip thepiezo-electric crystal between the rollers on its nodal line of electricpressure.

There may be more than one pair of rollers, a roller of each pairengaging one face of the piezoelectric crystal and another roller ofeach pair engaging the other face of the piezo-electric crystal, therollers on either face engaging the said face where parallellongitudinal lines intersect said nodal line.

The roller or rollers engaging one face of the piezo-electric crystalmay be unitary with or fixed upon a pin extending between and fixed ateach end to supporting members, while the roller or rollers engaging theother face may be unitary with or fixed upon apin extending between saidsupporting members, the ends of this last mentioned pin beingaccommodated in slots or grooves in said supporting member.

The spring is preferably so arranged as to bear down on the roller orrollers engaging the said other face at such an angle to the slots as tourge the roller both downwards and towards one face of ,the slots thusproviding a rigid holding without a too exacting width of slot.

Preferably the supporting members are attached to or are unitary with abase, from which box, at about half-way along the lengths of thesesprings an end wall between which, and the end 7 of the crystal a gaugemay be interposed so as to set the crystal relatively to the roller orrollers.

An exemplary embodiment of the invention is illustrated by theaccompanying drawing. Of the drawing,

\ Fig. 1 is a plan of the holder,

Fig. 2 is a section, seen in the direction of the rrow ii on line iL-iiFig. 1,

Fig. 3 is a view of a top cover of the holder, and

Fig. 4 is a view of a bottom cover,

Fig. 5 is a section, seen in the direction of arrow 12 on line V-V ofF18. 1, Fig. 6 is a plan view of the assembled holder,

Fig. 7 shows a lower pin,

side-'walls are provided with holes it, one hole in each wall, the holesbeing exactly opposite to each other and in line.

From top to bottom of each side-wall, on the inside, and also about halfway along the length of the side wall, a slot i1 is cut (or moulded),the slots in the two walls being exactly opposite to each other and inline with holes l6.

One of the end walls IQ, for convenience of description called the righthand end wall, has two narrow, shallow, slots like saw-cuts 20, althoughthey might, and generally would be otherwise produced, cut in the baseof it across the thickness. These slots are situated as far from eachother as may be required by the width of the crystal.

The lid i3 is pierced with a hole 2! which is situated somewhat nearerto the left hand end (using the same convention as above indicated) thanto the right hand end, and half-way from the front to the back. Throughthis hole is passed a. screw 22, Fig. 5, held in-place by means of a nut23, and holding in place, on the inside of the lid, a metal washer 24,and on the outside a connecting tag, 25.

A lower pin, it, Fig. 5, also shown separately in Fig. 7, preferablyground from stock, extends across from the front to the back wall of thebox. This pin is, preferably, of this shape, namely, first, a shortlength l of full diameter to fit in the hole in the back wall I5 01' thebox, then in succession a first short length 2 of slightly reduceddiameter, a shorter length l of full diameter, a medial length 4 ofreduced diameter, a second shorter length i of full diameter, a secondshort length 6 of reduced diameter, a second length I of full diameter,a short length 8 of greater reduced diameter, a short length 9 of fulldiameter, lengths 1, 8 and 9 being long enough to fit into the hole inthe front wall it of the box, a length ill of still greater reduceddiameter protruding from the box and'constituting a connecting pin. Thelower pin ll is fixed tightly in the holes I! with part i in the hole inthe back wall, and parts I, I and I in the hole in the front wall. Theyare sealed in their respective holes l6 against the entry 01' damp ordust. A pin 8|, Fig. 5, driven into a hole in the front wall l4,registering with part I of lower pin 26. serves to hold the latteragainst lateral movement. The two shorter lengths 3 and l of fulldiameter, the rollers referred to above, are situated equidistantly fromthe lengthwise medial line, V-V of Fig. 1, of the box, and are situatedsufilciently closely together to constitute seats for the crystal as canbe seen in Fig. 6.

The crystal 40 is placed loosely upon the lower pin and sits upon thefull-diameter shorter lengths 3 and which engage, approximately, itsmedia] nodal line of electrical pressure.

An upper pin, ll, Fig. 5, also shown separately in Fig. '7, preferablyground from stock, extends across from the front to the back wall of thebox. This pin is, preferably, of this shape, namely; first, a shortlength I of full diameter to fit loosely in the slot H in the back wallII of the box, then in succession a first short length H of slight- 1yreduced diameter, a shorter length III of full diameter, a medial lengthIVof reduced diameter, a second shorter length V of full diameter, asecond short length VI of reduced diameter, a second length V11 or fulldiameter to fit loosely in the slot il in the front wall ll of the box.The two shorter lengths III and V of full diameter, the rollers referredto above, are situated equldistantly from the lengthwise medial line ofthe box, and are situated s'uificiently closely together to be oppositethose, I and I, on the lower pin. This upper pin is placed loosely upon.the crystal, th rollers engaging approximately the medial nodal line ofelectrical pressure of the crystal.

A hair-pin shaped spring 42, Figs. 5, 8 and 9, of piano wire, has itstwo ends 41 inserted into the two slots in the right hand end wall (thebottom of the box having been previously fixed in place by means ofscrews II) and rests across the upper pin, 4 I, one leg resting on thefirst short length II and the other on the second short length VI oireduced diameter of this pin. The head or the spring extends somewhatabove the height of the walls of the box as indicated in Fig. 5 of thebroken line 42.

All the elements being in.place, the lid 01 the box is placed inposition, with the washer on the left hand under side in contact withthe head of the spring, and is screwed down by screws II. The crystal isnow spring held between the rollers, the spring having a downward and(conventionally) a left-hand component of pressure.

To make sure that the crystal is in proper position, that is with therollers engaging the nodal line of electrical pressure, the bottom coverl2 0! the box is now removed, and the crystal is centered by means of agauge ll, Fig. 10, which is inserted between the crystal and the endwall of the box. Alter-this adjustment, the bottom one face and theother roller engages the crystal on its other face, said one rollerbeing rigidly fixed to a support and the other being spring urgedtowards said one roller so as to grip the piezo-electric crystal betweenthe rollers on its nodal line of electric pressure.

2. A holder as claimed in claim 1, wherein there are a plurality ofrollers, one roller engagin one face of the piezo-electric crystal andanother roller engaging the other face of the piezo-electric crystal,the rollers on either face engaging the said face where parallellongitudinal lines intersect said nodal line.

3. A holder as claimed in claim 1, wherein one roller engaging one faceof the piezo-electric crystal is unitary with a pin extending betweenand fixed at each end to supporting members, while the other rollerengaging the other face is unitarywith a pin extending between saidsupporting members, the ends of this last mentioned pin beingaccommodated in slots in said supporting member.

4. A holder as claimed in claim 1. wherein one roller engaging one faceof the piezo-electric crystal is fixed upon a pin extending between andfixed at each end to supportin members, while the other roller engagingthe other face is fixed upon a pin extending between said supportingmembers, the ends of this last mentioned pin being accommodated ingrooves in said supporting member.

5. A holder as claimed in claim 1, wherein the urging spring is soarranged as to bear down on theroller engaging the said other face atsuch an angle to slots so as to urge the roller down and towards oneface of the slots thus providing a rigid holding without a too exactingwidth oi slot.

8. A holder as claimed in claim 1, wherein the support is attached toand is unitary with a base, from which rises an end wall between whichand the end of the crystal a gauge may be interposed so as to set thecrystal relatively to the rollers.

7. A piezo-electric crystal and holder, comprising said crystal and aholder including a recs tangular box of insulating material having twoend walls, front and back walls, and removable top and bottom covers, ametal pin extending across said box from the front to the back wallssaid pin having roller portions of enlarged diameter which serve asseats for said crystal, a second pin extending across said box from thefront to the back walls said pin having roller portions of enlargeddiameter which rest lightly upon said crystal. the first metal pin beingrigidly fixed in holes in said walls and the second metal pin beingfreely held in slots extending from the top oi said walls, and a hairpin spring having its ends accommodated in slots in one end wall and itslegs extending, one on each side of the crystal and resting on the upperpin, the spring being of such a length that its bridging piece. is abovethe tops of the walls and is pressed down by the top cover when in placeso as to provide downward and lateral components of pressure on saidupper pin.

8. A piezo-electric crystal and holder as claimed I in claim 7, whereinsaid top cover is Provided with a metallic terminal connection memberextending therethrough and making electrical connection with said springwhich is in electrical connection with one electrode of said crystalthrough said second mentioned pin.

9. A pine-electric crystal and bolder as claimed in claim 7, whereinsaid first mentioned pin is provided with a metallic extension,extending through a side wall other than an end wall and constituting anelectrical connection with the other electrode of said crystal.

10. A piezo-electric crystal and. holder as claimed in claim 7, whereinthe length of the crystal and of the box are such that the crystal maybe accurately situated with its line of pres- .allre gripped betweensaid rollers on said pins by means of a gauge of suitable thicknessinserted between an end of said crystal and an end of said box.

CHRISTOPHER SYDNEY COCKERm-L.

